Abdominal exerciser with rotatable seat and tandem pulley features

ABSTRACT

An abdominal exerciser has base and back frames pivotally mounted for movement between upright and recumbent positions, and a seat frame with cushion rotatable on the base frame. A low friction journal between the base and seat frames supports a user&#39;s weight. The journal is about 30 to 42% the distance from a rear end of the cushion to its front end so the user&#39;s coccyx is vertically aligned with the journal. Arms at each side of the base frame have a pair of extensions connected to either the base or seat frame, each with a U-shaped handhold lying in a plane at an acute angle of about 30 to 80 degrees to the horizontal. A pair of single pulleys or a pair of tandem pulleys are mounted near the rear of the base frame and are engaged by sleeve-covered springs for biasing the back frame toward the upright position.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates generally to the field of exercisedevices, and in particular, to a new and useful abdominal exerciser witha seat and a back supporting structure.

A wide variety of exercise devices and techniques are known forexercising the muscles of the stomach and back. Of these, the mostcommon is the sit-up or crunch which, however is also known to placeadverse pressure on the back and neck muscles.

U.S. Pat. No. 7,381,171 and D581,471, which are both incorporated hereby reference, disclose an abdominal exerciser co-invented by theinventors of the subject application. While effective for exercising themuscles of the stomach and back, the subject application disclosesimprovements that have been discovered as a result of use andunderstanding of the dynamics of the inventors' previous device.

A need thus still remains for further improvements in abdominal exercisedevices which enhance the exercising of the stomach and back muscleswhile avoiding adverse pressure on the back and neck muscles.

SUMMARY OF THE INVENTION

An object of the invention is to provide an abdominal exerciser that hasa base frame, a back frame pivotally mounted near a rear end of the baseframe for movement between upright and recumbent positions, at least oneback cushion connected to the back frame for supporting a user's back, aseat frame mounted for rotation on the base frame and a seat cushionfixed to the seat frame on which a user sits. A low friction journalbushing with a journal post rotatably mounted therein, is operativelyconnected between the base and seat frames for supporting the weight ofthe user. The bushing and post are about 30% to about 42% of thedistance from a rear end of the seat cushion to the front end of theseat cushion so that the user's coccyx is substantially verticallyaligned with the bushing and post when the user sits on the seat cushionand his or her back is resting against the back cushion. Arms at eachside of the base frame have a pair of extensions connected to either thebase or seat frame. Each arm has a U-shaped handhold lying in a planeextending at an acute angle of about 30 to about 80 degrees to thehorizontal plane. A pair of pulleys is mounted for rotation near a rearend of the base frame and engages springs with resilient sleevesthereover, the springs being connected between the base and back framesfor biasing the back frame toward the upright position.

A further object of the invention is to provide an abdominal exercisedevice that comprises: a base frame for lying in a horizontal plane onthe floor, the base frame having a pair of side members and a crossmember connected between the side members of the base frame; a backframe having a pair of side members pivotally mounted near respectiverear ends of the respective side members of the base frame for movementbetween a forward upright position and a rearward recumbent position; aplurality of back cushions connected between and spaced along the sidemembers of the back frame; an H-shaped seat frame having front and rearmembers and a cross member connected between the front and rear members;a seat cushion fixed to the seat frame and resting on the front, rearand cross members of the seat frame, the seat cushion having a front endand a rear end; a low friction journal bushing having a verticallyextending bore and being connected to the cross member of one of thebase and seat frames; a journal post connected to the cross member ofthe other of the base and seat frames and received for rotation in thelow friction journal bushing so that the seat cushion may rotate withrespect to the base frame, a support area of the cross member around thejournal post and to which the journal post is connected, being inweight-bearing contact with the low friction journal bushing forsupporting the weight of a user sitting on the seat cushion, thelocation of the low friction journal bushing and the journal postreceived therein, being from about 30% to about 42% of the distance fromthe rear end of the seat cushion to the front end of the seat cushion sothat when a user is sitting on the seat cushion with the users backagainst the back cushions, the coccyx of the user is substantiallyvertically aligned with the low friction journal bushing and journalpost received therein; an arm at each side of the base frame, each armhaving a pair of extensions connected to one of the base frame and theseat frame, each arm including a U-shaped handhold lying in a plane thatextends at an acute angle of about 30 degrees to about 80 degrees to thehorizontal plane, with the handholds of the arms on opposite sides ofthe base frame extending outwardly from each other for increasingavailable room for a user sitting on the seat cushion, and access to thehandholds by the user; a pulley mounted for rotation at each side of thebase frame near a rear end of the base frame; a tension spring connectedbetween the base frame and the back frame side members for biasing theback frame toward the forward upright position; and a resilient sleevecovering each spring, each resilient sleeve being engaged with one ofthe pulleys.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side, front, top perspective view of an abdominal exercisedevice embodying the present invention, in an upright forward and readyposition awaiting use by a user for exercising the user's abdominal andback muscles;

FIG. 2 is a view of the device similar to FIG. 1 but with the back frameand cushions moved from an upright forward position toward a rearwardrecumbent position for exercising the back muscles of a user (not shown)sitting on the device;

FIG. 3 is a view of the device similar to FIG. 2 with the back frame andcushions moved toward the recumbent position and with a seat frame andcushion of the device rotated to an extreme left position for furtherexercising the side muscles of the users abdomen;

FIG. 4 is a view of the device similar to FIG. 3 but with the seat frameand cushion rotated to an extreme right position for further exercisingthe side muscles of the users abdomen;

FIG. 5 is a front elevational and slightly perspective view of thedevice for illustrating the non-perpendicular, angled extension ofU-shaded handholds of arms of the device, for improved room on the seatcushion and improved access to the handholds;

FIG. 6 is a side elevational and slightly perspective view of the deviceshowing a user sitting on the seat cushion to illustrate the location ofa low friction, weight-bearing journal of the device and its verticalalignment with the base of the user's spine;

FIG. 7 is a top plan view of the device that better illustrates theposition of the journal with respect to front and rear ends of the seatcushion;

FIG. 8 is an exploded perspective view of the abdominal exercise deviceof the invention;

FIG. 9 is a top perspective view of an alternate embodiment of thedevice with the arms fixed to the seat frame rather than to the baseframe;

FIG. 10 is an enlarged side elevational view of a locking pin forholding the seat frame in a non-rotatable position of the base frame;

FIG. 11 is an enlarged, exploded, sectional view of the journal area ofthe device; and

FIG. 12 is a partial, rear, perspective view of a further embodiment ofthe invention with tandem pulleys and resilient sleeve covered springsfor each side of the base and back frames plus a safety band forcovering the pulleys and springs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, in which like reference numerals are usedto refer to the same or similar elements, FIGS. 1 and 8 illustrate anabdominal exercise device 10 that comprises a base frame 12 for lying ina horizontal plane on the floor, the base frame having a pair of sidemembers 12 a and 12 b and a cross member 12 c connected, e.g. bywelding, between the side members of the base frame. Members 12 a, 12 band 12 c and preferably square of rectangular cross-sectioned metaltubes. A back frame 14 having a pair of side members 14 a and 14 b ispivotally mounted on a pair of ears 13 at the top of, and nearrespective rear ends of the side members 12 a and 12 b of the base framefor movement between a forward upright position shown in FIG. 1, and arearward recumbent position shown in FIG. 2. A bolt 15 extends throughaligned holes in the pair of ears 13 on each side of base frame 12, tohold back frame side members 14 a, 14 b to the base frame, and to formthe axle for one or two pulleys 60 mounted for rotation to each side ofthe base frame 12. A plurality of back cushions 20, each in the form ofa rotatable foam rubber roller, are connected between and spaced alongthe side members 14 a and 14 b of the back frame 14. The lowest rollercushion 20 is mounted for rotation on the same axis on which theopposite bolts 15 extend.

An H-shaped seat frame 16 having front and rear members 16 a and 16 b,has a cross member 16 c that is connected, e.g. by welding, between thefront and rear members. A padded seat cushion 30 is fixed to the seatframe 16 and resting on the front, rear and cross members of the seatframe. The seat cushion has a front end 30 a and a rear end 30 b.

A low friction journal bushing 40, shown also in FIG. 11, is made forexample from low friction nylon, has a vertically extending bore 40 aand is fixed to the cross member 12 c, e.g. by extending through a borein the cross member and by having a small lower flange ring 40 a and alarge upper flange ring 40 b. The upper flange ring 40 b has a broadflat upper annular bearing surface. A journal post 42 is connected, e.g.by welding, to the cross member 16 c of the seat frame 16 and isreceived for rotation in the low friction journal bushing bore 40 a sothat the seat cushion 30 may rotate with respect to the base frame 12.

A support area of the seat frame cross member 16 c that is immediatelyaround the journal post 42, is in weight-bearing contact with the uppersurface of the upper flange 14 b of low friction journal bushing 40, forsupporting all of the weight of a user 100 sitting on the seat cushionas shown in FIG. 6. As shown in FIG. 7, The location of the low frictionjournal bushing 40 and the journal post 42 received therein, is adistance C from the rear end 30 b of the seat cushion 30, that is fromabout 30% to about 42% (preferable about 33 to 39%) of the totaldistance B from the rear end 30 b of the seat cushion to the front end30 a of the seat cushion 30. Because of this important placement of therotation journal for the seat frame 16 and its cushion 30, when a user100 is sitting on the seat cushion 30 with the user's back against theback cushions 20, the user's coccyx at the lower end of his or her spine102, is substantially vertically aligned with the low friction journalbushing 40 and journal post 42 received therein, as shown by the arrow Xin FIG. 6. In this way virtually all the user's weight is centered onthe upper surface of the bushing flange 40 b so that no other weightbearing mechanism is needed for allowing free and easy rotation of theseat cushion 30 on the base frame 12. In the embodiment shown, forexample, the dimension of distant C is about 4 inches for a total frontto back dimension B of about 11 inches for seat cushion 30.

The same weight-bearing function would be achieved in the alternateembodiment of the invention where the bushing 40 is mounted to the crossmember 16 c of the seat frame 16 and the post 42 is mounted to the crossmember 12 c of the base frame 12.

An arm 50 is also provided at each side of the base frame 12, each armhaving a pair of extensions 50 a and 50 b that are detachably connectedto side tubes 12 d and 12 e extending from the side members 12 a and 12b of base frame 12. As best shown in FIGS. 5 and 8, the side tubes 12 eare circular cross sectioned metal tubes welded to the outside surfacesof side member 12 a and 12 b, while side tubes 12 d are actually thesideways opposite extensions of a front member, circular cross sectionedmetal tube of base frame 12, welded to and across the front ends of theside members 12 a and 12 b.

Each arm 50 includes a U-shaped handhold 50 c best shown in FIG. 5, tolie in a plane that extends at an acute angle A of about 30 degrees toabout 80 degrees to the horizontal plane with the handholds 50 c of thearms 50 on opposite sides of the base frame extending outwardly fromeach other for increasing available room for a user sitting on the seatcushion 30, and provided better access to the handholds by the user'shands. The even more preferred range of angle A is about 50 to 70degrees. Detachable connection of the arms 50 to the base frame 12 isachieved by having the round cross sectioned tubes making arm extensions50 a and 50 b, smaller in diameter than the round cross sectioned tubesmaking base frame extensions 12 d and 12 e, so that the arm tubes fitinside the base frame tubes. Locking of the arms 50 in position onopposite sides of base frame 12 is achieved by a pair of outwardlyspring-loaded hemispheres 50 d near the inside ends of front extensions50 a, that snap into opposite holes 12 h near the end of the base frameextensions 12 d. No separated locking is needed for the rear extensions50 b.

In this embodiment the arms 50 are fixed to the base frame 12 and theuser can hold the arms at the handholds 50 c to help rotate the user'swaist and thus rotate the seat cushion 30 on the base frame whilecycling the back frame 14 between the upright and recumbent positions totarget the side muscles of the user's abdomen. In another embodiment ofthe invention shown in FIG. 9, arm extensions 50 a and 50 b aredetachably connected to the opposite tubular ends of the front and rearmembers 16 a, 16 b of the seat frame 16, so that the arms 50 rotate withthe seat cushion 30 for a different set of exercise dynamics.

In order to lock seat frame 16 and its cushion 30 in a centered andnon-rotating position shown in FIGS. 1 and 2, the rear seat frame member16 b has one tubular end 16 d that projects beyond the seat cushion 30and has a vertical locking hole that aligns with a vertical locking hole12 j that is in the rear arm extension 50 b but may alternatively be inthe rear base frame extension 12 in the embodiment of FIG. 8, butespecially when the arms are connected to the seat frame in theembodiment of FIG. 9. A locking pin 70 having a shaft 70 a and a ballhandle 70 b has its shaft 70 a inserted into the aligned locking holesto lock the seat frame in place. As best shown in FIG. 10, an annulargroove 70 c near the top end of shaft 70 a resists accidental withdrawalof the locking pin 70 as the user exercises by catching the sheet metalmaterial of the hollow tubes making up the seat and base frames at thelocking holes. By the action of gravity and with the help of the extraweight of ball handle 70 a, the pin 70 is randomly cause to fall backinto its locked position rather than being pushed out of the lockingholes during an exercise session. With the locking pin pulled out of thelocking holes as shown in FIGS. 3 and 4, the seat cushion 30 can berotated to the left and right as the user rotates his or her waist forenhancing the exercise routine.

One pulley 60 is mounted for rotation at each side of the base frame 12near a rear end of the base frame about the bolts 15. A tension spring80 has an eye 84 at one end engaged onto a spring post 14 c extendingfrom the back frame side member 14 a, and an eye 85 on its opposite endengaged onto a spring post 12 f extending from the base frame sidemember 12 a, for biasing the back frame 14 toward the forward uprightposition shown in FIGS. 1 and 8. Threaded knobs 86 are screwed onto thethreaded ends of spring posts 14 c and 12 f to secure the springs 80 onplace. A resilient, e.g. foam rubber sleeve 82 covers each spring 80 andeach resilient sleeve-covered spring is engaged with the groove of oneof the pulleys 60.

Another embodiment of the invention is shown in FIG. 12 where a pair oftandem pulleys 60, 60 mounted for rotation on a longer bold 15 at eachside of the base frame and tension springs 80 connected between the baseframe and the back frame side members each with a resilient sleeve 82covering each spring, is engaged with each pulley 60 for biasing theback frame toward the forward upright position with twice the strength.This adds more resistance to each back movement toward the recumbentposition for a stronger workout. The tandem pulleys can be used with theprior abdominal exercisers of U.S. Pat. No. 7,381,171 and D581,471, orwith the improvements of FIGS. 1-11. As also shown in FIG. 12 and alsousable with the tandem pulleys and/or with the improvements of FIGS.1-11, is an elastic fabric band 90 that has a width that is wide enoughto cover the single pulley 60 or the double pulleys 60, 60, and acircumference that is slightly less than the path around the pulleys 60,the spring posts and the springs 80 with covering sleeves 82. In use theband 90 is stretched over the pulleys and engaged sleeve-coveredsprings, and is held in place by one or a pair of hook-and-loop coveredstraps 92 that are threaded behind the one or two springs 80, atlocations over and, if two straps are use, under the area of engagementbetween the sleeves 82 and the grooves of the pulleys 60, and then backover the band until the straps are engage to themselves at their bases,and held in place be the hook-and-loop action on there touchingsurfaces. The use of these elastic bands 90 serve two purposes. Firstly,they are a safety measure in case any part of the springs or theirattachments break, to keep all parts confined inside the elastic band sonothing flies away for the device. Secondly the elastic bands reduce ormuffle any noise created by the springs and pulleys as the device iscycled between upright and recumbent positions during an exercisecession.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. An abdominal exercise device (10) comprising: abase frame (12) for lying in a horizontal plane on the floor, the baseframe having a pair of side members (12 a, 12 b) and a cross member (12c) connected between the side members of the base frame; a back frame(14) having a pair of side members (14 a, 14 b) pivotally mounted nearrespective rear ends of the respective side members (12 a, 12 b) of thebase frame for movement between a forward upright position and arearward recumbent position; a plurality of back cushions (20) connectedbetween and spaced along the side members (14 a, 14 b) of the back frame(14); an H-shaped seat frame (16) having front and rear members (16 a,16 b) and a cross member (16 c) connected between the front and rearmembers; a seat cushion (30) fixed to the seat frame (16) and resting onthe front, rear and cross members of the seat frame, the seat cushionhaving a front end and a rear end; a low friction journal bushing (40)having a vertically extending bore and being connected to the crossmember (12 c, 16 c) of one of the base and seat frames (12, 16); ajournal post (42) connected to the cross member (12 c, 16 c) of theother of the base and seat frames (12, 16) and received for rotation inthe low friction journal bushing (40) so that the seat cushion (30) mayrotate with respect to the base frame (12), a support area of the crossmember around the journal post and to which the journal post isconnected, being in weight-bearing contact with the low friction journalbushing (40) for supporting the weight of a user sitting on the seatcushion, the location of the low friction journal bushing (40) and thejournal post (42) received therein, being from about 30% to about 42% ofthe distance from the rear end of the seat cushion to the front end ofthe seat cushion so that when a user is sitting on the seat cushion (30)with the users back against the back cushions (20), the coccyx of theuser is substantially vertically aligned with the low friction journalbushing (40) and journal post (42) received therein; an arm (50) at eachside of the base frame, each arm having a pair of extensions (50 a, 50b) connected to one of the base frame and the seat frame, each armincluding a U-shaped handhold (50 c) lying in a plane that extends at anacute angle of about 30 degrees to about 80 degrees to the horizontalplane with the handholds (50 c) of the arms (50) on opposite sides ofthe base frame extending outwardly from each other for increasingavailable room for a user sitting on the seat cushion, and access to thehandholds by the user; a pulley mounted for rotation at each side of thebase frame near a rear end of the base frame; a tension spring connectedbetween the base frame and the back frame side members for biasing theback frame toward the forward upright position; and a resilient sleevecovering each spring, each resilient sleeve engaged with one of thepulleys.
 2. The device of claim 1, wherein the side members (12 a, 12 b)of the base frame (12) each include a tubular side extension (12 d, 12e), the extensions (50 a, 50 b) of each arm (50) being detachablyattached to the tubular side extension on each respective side of thebase frame (12) so that the arms are fixed to the base frame when theseat frame rotates.
 3. The device of claim 1, wherein the extensions (50a, 50 b) of each arm (50) are detachably attached to ends of therespective front and rear members (16 a, 16 b) of the seat frame (16) oneach respective side of the seat frame so that the arms rotate with therotation of the seat frame.
 4. The device of claim 1, including a pairof tandem pulleys mounted for rotation at each side of the base frameand a tension spring connected between the base frame and the back frameside members each with a resilient sleeve covering each spring, engagedwith each pulleys for biasing the back frame toward the forward uprightposition.
 5. The device of claim 1, wherein the handhold (50 c) lying ina plane that extends at an acute angle of about 50 degrees to about 70degrees to the horizontal plane.
 6. The device of claim 1, wherein thelocation of the low friction journal bushing (40) and the journal post(42) received therein, is from about 33% to about 39% of the distancefrom the rear end of the seat cushion to the front end of the seatcushion.
 7. The device of claim 1, wherein the rear member of the seatframe includes a seat frame extension (16 d) that extends beyond theseat cushion (30), locking holes in the seat frame extension and in thebase frame or in one arm extension, that are aligned when the seatcushion is rotation to a centered position, and a locking pin forinsertion into the aligned locking holes for fixing the seat cushion inthe center position.
 8. The device of claim 1, wherein the rear memberof the seat frame includes a seat frame extension (16 d) that extendsbeyond the seat cushion (30), locking holes in the seat frame extensionand in the base frame or in one arm extension, that are aligned when theseat cushion is rotation to a centered position, and a locking pin forinsertion into the aligned locking holes for fixing the seat cushion inthe center position, the locking pin including an upper handle that islarger in at least one dimension than the locking holes, and a shaftthat is smaller in diameter than the locking holes so that the shaft canextend into the aligned locking hole, the shaft including an annulargroove near the upper handle.
 9. The device of claim 1, including anelastic band with at least one hook-and-loop covered strap extendingfrom one edge of the band for engagement of the band onto the pulley andsleeve covered spring on each side of the base and back frames.
 10. Anabdominal exerciser comprising: a base frame; a back frame pivotallymounted near a rear end of the base frame for movement between uprightand recumbent positions; at least one back cushion connected to the backframe for supporting a user's back; a seat frame mounted for rotation onthe base frame; a seat cushion fixed to the seat frame on which a usersits; a low friction journal bushing connected the base frame, a journalpost connected to the seat frame and rotatable mounted in the bushingfor rotation of the seat frame and cushion on the base frame; the lowfriction bushing supporting the weight of a user sitting on the seatcushion and the journal post being located at about 30% to about 42% ofa distance from a rear end of the seat cushion to the front end of theseat cushion so that the coccyx of a user sitting on the seat cushion issubstantially vertically aligned, with the bushing and post; an armconnected at each side of the base frame, each arm having a pair ofextensions connected to the base frame; each arm having a U-shapedhandhold lying in a plane extending at an acute angle of about 30 toabout 80 degrees to a horizontal plane on which the base rests, a pairof pulleys mounted for rotation near a rear end of the base frame and onopposite sides of the base frame; a springs with a resilient sleevethereover engaged to each pulley, the springs being connected betweenthe base and back frames for biasing the back frame toward the uprightposition.
 11. The device of claim 10, wherein side members of the baseframe include tubular side extensions, the extensions of each arm beingdetachably attached to the tubular side extension on each respectiveside of the base frame so that the arms are fixed to the base frame whenthe seat frame rotates, the handhold lying in a plane that extends at anacute angle of about 50 degrees to about 70 degrees to the horizontalplane, the location of the low friction journal bushing and the journalpost received therein, being from about 33% to about 39% of the distancefrom the rear end of the seat cushion to the front end of the seatcushion, a rear member of the seat frame including a seat frameextension that extends beyond the seat cushion, locking holes in theseat frame extension and in the base frame or one of the arm extensions,that are aligned when the seat cushion is rotation to a centeredposition, and a locking pin for insertion into the aligned locking holesfor fixing the seat cushion in the center position, the locking pinincluding an upper handle that is larger in at least one dimension thanthe locking holes, and a shaft that is smaller in diameter than thelocking holes so that the shaft can extend into the aligned lockinghole, the shaft including an annular groove near the upper handle. 12.An abdominal exercise device comprising: a base frame for lying in ahorizontal plane on the floor, the base frame having a pair of sidemembers; a back frame having a pair of side members pivotally mountednear respective rear ends of the side members of the base frame formovement between a forward upright position and a rearward recumbentposition; a plurality of back cushions connected between and spacedalong the side members of the back frame; a seat cushion mounted to thebase frame; an arm detachably connected to each side member of the baseframe and on opposite sides of the seat cushion; a pair of side-by-sidetandem pulleys mounted for rotation at each side member of the baseframe near a rear end of the base frame; a pair of tension springsconnected between the base frame and the back frame side members on eachside of the base and back frames for biasing the back frame toward theforward upright position; and a resilient sleeve covering each spring,each resilient sleeve engaged with one of the pulleys.
 13. The device ofclaim 12, wherein the side members (12 a, 12 b) of the base frame (12)each include a tubular side extension (12 d, 12 e), the extensions (50a, 50 b) of each arm (50) being detachably attached to the tubular sideextension on each respective side of the base frame (12) so that thearms are fixed to the base frame when the seat frame rotates.
 14. Thedevice of claim 12, wherein the extensions (50 a, 50 b) of each arm (50)are detachably attached to ends of the respective front and rear members(16 a, 16 b) of the seat frame (16) on each respective side of the seatframe so that the arms rotate with the rotation of the seat frame. 15.The device of claim 12, including a pair of tandem pulleys mounted forrotation at each side of the base frame and a tension spring connectedbetween the base frame and the back frame side members each with aresilient sleeve covering each spring, engaged with each pulleys forbiasing the back frame toward the forward upright position.
 16. Thedevice of claim 12, wherein the handhold (50 c) lying in a plane thatextends at an acute angle of about 50 degrees to about 70 degrees to thehorizontal plane.
 17. The device of claim 12, wherein the location ofthe low friction journal bushing and the journal post received therein,is from about 33% to about 39% of the distance from the rear end of theseat cushion to the front end of the seat cushion.
 18. The device ofclaim 12, wherein the rear member of the seat frame includes a seatframe extension that extends beyond the seat cushion, locking holes inthe seat frame extension and in the base frame or in one of the armextension, that are aligned when the seat cushion is rotation to acentered position, and a locking pin for insertion into the alignedlocking holes for fixing the seat cushion in the center position. 19.The device of claim 12, wherein the rear member of the seat frameincludes a seat frame extension that extends beyond the seat cushion,locking holes in the seat frame extension and in the base frame or inone of the arm extensions, that are aligned when the seat cushion isrotation to a centered position, and a locking pin for insertion intothe aligned locking holes for fixing the seat cushion in the centerposition, the locking pin including an upper handle that is larger in atleast one dimension than the locking holes, and a shaft that is smallerin diameter than the locking holes so that the shaft can extend into thealigned locking hole, the shaft including an annular groove near theupper handle.
 20. The device of claim 12, including an elastic band withat least one hook-and-loop covered strap extending from one edge of theband for engagement of the band onto the pulley and sleeve coveredspring on each side of the base and back frames.